Conditional Statements in Java ICSE Class 9: if, if-else, Ladder, Nested if and switch

What Conditional Statements in Java is about

Weightage: CISCE publishes no chapter weightage and no question-paper layout for ICSE Class 9 Computer Applications. Class IX is examined by your school: one 100-mark theory paper of 2 hours, plus 100 marks of internal assessment (at least 15 programming assignments and a written project on ethical computing). This is topic 8 of the 2028 syllabus.Source: CISCE ICSE 2028 Computer Applications syllabus, Class IX

Key concepts

if and if-else

if statement: runs a statement (or block) only when the condition is true.
if (condition)
{
statements;
}

if-else statement: chooses between two alternatives.
if (condition)
statement1; // when true
else
statement2; // when false

Rules:

• The condition must be a boolean expression in brackets: (marks >= 40). Writing if (x = 5) is a compile-time error in Java (int cannot be converted to boolean); use ==.
• Without braces, only the first statement after if (or else) belongs to it. Use braces { } for more than one statement.
• No semicolon straight after if (condition): if (a > b); makes an empty statement, and the next line always runs.

Example (as run in this study guide): int x = 7; if (x % 2 == 0) System.out.println("Even"); else System.out.println("Odd"); prints Odd.

Braces trap (as run): int m = 10; if (m > 5) m = m + 1; m = m * 2; gives 22: only m = m + 1 is controlled by if; m = m * 2 always runs.

Worked example

(2 marks) Give the output: int m = 4; if (m > 5) m = m + 1; m = m * 2; System.out.println(m);

Try it first, then show the solutionSolution

1. Without braces, only m = m + 1 belongs to the if; 4 > 5 is false, so it is skipped - 1 mark.
2. m = m * 2 always runs: 8 - 1 mark.

Answer: 8

The if-else-if ladder

Used when one of several conditions must be chosen. Conditions are tested from the top; the first true one runs and the rest are skipped. The final else runs if none is true.

if (cond1) s1;
else if (cond2) s2;
else if (cond3) s3;
else s4;

Slab billing example (hypothetical tariff, as run in this study guide):
Units up to 100: Rs 5.00 per unit; next 100: Rs 6.50; next 100: Rs 8.00; above 300: Rs 10.00.
if (u <= 100)
amt = u * 5.0;
else if (u <= 200)
amt = 100 * 5.0 + (u - 100) * 6.5;
else if (u <= 300)
amt = 100 * 5.0 + 100 * 6.5 + (u - 200) * 8.0;
else
amt = 100 * 5.0 + 100 * 6.5 + 100 * 8.0 + (u - 300) * 10.0;
Results: 80 units → Rs 400.0; 250 units → Rs 1550.0; 340 units → Rs 2350.0.

Because the ladder stops at the first true condition, the second test need not repeat u > 100.

Worked example

(2 marks) Using the slab tariff above, calculate the bill for 250 units, showing the slabs.

Try it first, then show the solutionSolution

1. First 100 × 5.00 = 500; next 100 × 6.50 = 650 - 1 mark.
2. Remaining 50 × 8.00 = 400; total = 1550 - 1 mark.

Answer: Rs 1550.0

Nested if and the dangling else

A nested if is an if (or if-else) inside another if or else. It is used when a second decision depends on the first.

Largest of three (as run in this study guide with p = 15, q = 25, r = 20):
if (p > q)
{
if (p > r) big = p; else big = r;
}
else
{
if (q > r) big = q; else big = r;
}
Output: Largest = 25

Dangling else rule: an else belongs to the nearest unmatched if above it, whatever the indentation.
int a = 5, b = 10;
if (a > b)
if (a > 0)
System.out.println("A");
else
System.out.println("B");
System.out.println("C");
The else pairs with if (a > 0). Since a > b is false, the whole inner if-else is skipped, and only C is printed (as run).
Use braces to make the intended pairing clear.

Worked example

(2 marks) In the dangling-else code above, what is printed if a = 15 and b = 10?

Try it first, then show the solutionSolution

1. a > b is true, so the inner if-else runs - 1 mark.
2. a > 0 is true: prints A; then C is printed (outside the if) - 1 mark.

Answer: A
C

switch-case, break and default

switch selects one of many branches by comparing a single value with constant case labels.
switch (expression)
{
case value1: statements; break;
case value2: statements; break;
default: statements;
}

Rules:

• The expression may be of type int, char, short, byte (or String); not double, float, long or boolean.
• Case labels must be constants (literals), not ranges or conditions, and must not repeat.
• break ends the switch; control passes to the statement after it.
• default runs when no case matches; it is optional and may be placed anywhere, though usually last.
• Several cases can share statements: case 'a': case 'e': case 'i': case 'o': case 'u': System.out.println("Vowel"); break;

switch vs if-else-if:
1. switch tests only equality with constants; if can test any condition (ranges, &&, ||).
2. switch works on int, char, String (and smaller integer types); if works with any boolean expression.
3. switch is neater for menus with many fixed choices.

Worked example

(2 marks) State two differences between switch-case and the if-else-if ladder.

Try it first, then show the solutionSolution

1. switch checks equality with constant values only; if can test ranges and logical conditions - 1 mark.
2. switch works only with int, char, String, byte, short; if works with any boolean expression including double comparisons - 1 mark.

Answer: (1) switch compares one value for equality with constant case labels, whereas if-else-if can test any condition, such as ranges and combined conditions. (2) switch accepts only integer types, char and String, whereas if works with any boolean expression, including those on double values.

Fall through

If a case has no break, control 'falls through' into the following case(s) and runs their statements too, until a break or the end of the switch.

As run in this study guide:
switch (n)
{
case 1: System.out.print("One ");
case 2: System.out.print("Two ");
case 3: System.out.print("Three ");
break;
case 4: System.out.print("Four ");
default: System.out.print("Other ");
}
n = 2 prints: Two Three
n = 4 prints: Four Other

Fall through is useful when several cases share an action (vowels), but a forgotten break is a common logical error.

Worked example

(2 marks) Using the switch above, what is printed for n = 1 and for n = 7?

Try it first, then show the solutionSolution

1. n = 1: One, falls to Two and Three, then break - 1 mark.
2. n = 7: no case matches; default prints Other - 1 mark.

Answer: n = 1: One Two Three
n = 7: Other

Menu-driven programs and System.exit(0)

A menu-driven program displays a list of choices, accepts the user's choice and performs the matching task, usually with switch.

System.exit(0) terminates the program immediately; no further statements run. The argument 0 indicates normal termination (a non-zero value signals an abnormal end).

Program (as run in this study guide):
import java.util.*;
class Menu
{
public static void main(String args[])
{
Scanner sc = new Scanner(System.in);
System.out.println("1. Area of a circle");
System.out.println("2. Area of a square");
System.out.println("3. Exit");
System.out.print("Enter your choice: ");
int ch = sc.nextInt();
switch (ch)
{
case 1:
System.out.print("Radius: ");
double r = sc.nextDouble();
System.out.println("Area = " + Math.round(Math.PI * r * r * 100) / 100.0);
break;
case 2:
System.out.print("Side: ");
double s = sc.nextDouble();
System.out.println("Area = " + s * s);
break;
case 3:
System.out.println("Goodbye");
System.exit(0);
default:
System.out.println("Invalid choice");
}
System.out.println("End of menu");
}
}
Runs: choice 1, radius 7 → Area = 153.94 then End of menu; choice 3 → Goodbye only (System.exit(0) stops the program, so neither default nor End of menu runs); choice 5 → Invalid choice, End of menu.
(Math.PI is the constant π stored in the Math class.)

Worked example

(2 marks) In the Menu program, case 3 has no break. Why does 'Invalid choice' not appear when 3 is entered?

Try it first, then show the solutionSolution

1. System.exit(0) ends the program at once - 1 mark.
2. So control never falls through to default or reaches 'End of menu' - 1 mark.

Answer: System.exit(0) terminates the whole program immediately, so execution never falls through into default and the final println is never reached; only Goodbye is printed.

Conditional Statements in Java in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• if, if-else, if-else-if Ladder and Nested if with Output Tracing
• switch-case, break, default, Fall Through and Menu-Driven Programs

Conditional Statements in Java: syntax and key facts

if forms

if; if-else; if-else-if ladder; nested if

else pairs with the nearest unmatched if.

switch

switch (int/char/String) { case const: ...; break; default: ... }

No double, long or boolean; constants only.

Fall through

Missing break → next case's statements also run

Until break or end.

Exit

System.exit(0) → terminate the program normally

Nothing after it runs.

Leap year

(y % 4 == 0 && y % 100 != 0) || y % 400 == 0

2000 leap, 1900 not.

How the school exam asks Conditional Statements in Java

The question patterns to expect, and the method that works for each.

Tricks to remember Conditional Statements in Java

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Else hugs the nearest if

  An else always belongs to the closest if above that has no else.

  Use it when: Dangling else.

• switch likes ICS

  Int, Char, String (and byte, short): never double, float, long or boolean.

  Use it when: switch data types.

• Break the fall

  Without break, you fall into the next case.

  Use it when: Fall through.

Conditional Statements in Java: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section B style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 7-mark question split into 2 + 3 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Conditional Statements in Java

The slips examiners see most often, and what to write instead.

• ✗Mistake: Ladder in the wrong order

  Lowest condition written first.

  Wrong working

  if (m >= 40) ... else if (m >= 90) ...

  Right working

  if (m >= 90) ... else if (m >= 75) ... else if (m >= 40) ...

  ✓Do this: With >=, test the highest value first.

  Usually costs: 2 to 4 marks.

• ✗Mistake: Missing break in switch

  Forgetting fall through.

  ✓Do this: End every case with break unless fall through is intended.

  Usually costs: 1 to 3 marks.

• ✗Mistake: Using = instead of ==

  Mathematical habit.

  Wrong working

  if (x = 5)

  Right working

  if (x == 5)

  ✓Do this: == compares; = assigns.

  Usually costs: 1 mark.

• ✗Mistake: Ranges in case labels

  Treating switch like if.

  Wrong working

  case m >= 90:

  Right working

  Use if-else-if for ranges.

  ✓Do this: Case labels must be constants.

  Usually costs: 1 to 2 marks.

• ✗Mistake: Missing braces around several statements

  Indentation is trusted.

  ✓Do this: Put { } round every block of more than one statement.

  Usually costs: 1 to 2 marks.

Practice questions on Conditional Statements in Java

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which statement is used to terminate a Java program immediately?
   (a) break;
   (b) System.exit(0);
   (c) return 0;
   (d) default;

   Hint

   Whole program.

   Answer

   (b) System.exit(0);

2. Q2 · 1 mark · MCQExam level

   In a switch, the default case runs when:
   (a) always
   (b) the first case matches
   (c) no case matches
   (d) break is missing

   Hint

   Fallback.

   Answer

   (c) no case matches

3. Q3 · 2 marks · Very short answerHarder exam level

   Give the output: char c = 'e'; switch (c) { case 'a': case 'e': case 'i': case 'o': case 'u': System.out.println("Vowel"); break; default: System.out.println("Consonant"); }

   Hint

   Shared cases.

   Answer

   Vowel

4. Q4 · 2 marks · Short answerHOTS / competency

   Find the error: if (marks >= 40); System.out.println("Pass"); What happens when marks = 25?

   Hint

   Semicolon after the condition.

   Answer

   The semicolon after the condition ends the if with an empty statement, so println("Pass") is not controlled by the if. For marks = 25 it still prints Pass (a logical error).

5. Q5 · 2 marks · Very short answerExam level

   Rewrite using the ternary operator: if (n % 2 == 0) s = "Even"; else s = "Odd";

   Hint

   ?:

   Answer

   s = (n % 2 == 0) ? "Even" : "Odd";

6. Q6 · 2 marks · Very short answerHarder exam level

   Write a nested if to print the largest of three numbers p, q, r. What is printed for p = 15, q = 25, r = 20?

   Hint

   Compare p and q first.

   Answer

   if (p > q) { if (p > r) big = p; else big = r; } else { if (q > r) big = q; else big = r; } System.out.println("Largest = " + big); Output: Largest = 25

7. Q7 · 15 marks · Long answerHarder exam level

   Write a menu-driven program: 1 for the area of a circle (radius input, rounded to 2 decimal places), 2 for the area of a square (side input), 3 to exit using System.exit(0); print 'Invalid choice' otherwise.

   Hint

   switch with break; default.

   Answer

   import java.util.*;
   class Menu
   {
   public static void main(String args[])
   {
   Scanner sc = new Scanner(System.in);
   System.out.println("1. Area of a circle");
   System.out.println("2. Area of a square");
   System.out.println("3. Exit");
   System.out.print("Enter your choice: ");
   int ch = sc.nextInt();
   switch (ch)
   {
   case 1:
   System.out.print("Radius: ");
   double r = sc.nextDouble();
   System.out.println("Area = " + Math.round(Math.PI * r * r * 100) / 100.0);
   break;
   case 2:
   System.out.print("Side: ");
   double s = sc.nextDouble();
   System.out.println("Area = " + s * s);
   break;
   case 3:
   System.out.println("Goodbye");
   System.exit(0);
   default:
   System.out.println("Invalid choice");
   }
   System.out.println("End of menu");
   }
   }
   Sample runs (as run): choice 1 with radius 7 prints Area = 153.94 and End of menu; choice 3 prints Goodbye only; choice 5 prints Invalid choice and End of menu.

8. Q8 · 2 marks · Very short answerHarder exam level

   A shop gives a 10% discount on bills over Rs 5,000 and 5% on bills over Rs 2,000 (and up to 5,000). Write the if-else-if statements to compute the net amount for bill b.

   Hint

   Larger threshold first.

   Answer

   if (b > 5000) net = b - b * 10 / 100.0;
   else if (b > 2000) net = b - b * 5 / 100.0;
   else net = b;

9. Q9 · 2 marks · Short answerHOTS / competency

   Why is it a good idea always to include a default case in a menu-driven switch?

   Hint

   Unexpected input.

   Answer

   Users may type a choice that is not on the menu. Without default the program silently does nothing; with default it can tell the user 'Invalid choice', making the program clear and robust.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.Which if does an else belong to?Show answer

   The nearest unmatched if above it.

2. 2.What does break do in switch?Show answer

   Exits the switch.

3. 3.What happens without break?Show answer

   Fall through into the next case.

4. 4.What does System.exit(0) do?Show answer

   Terminates the program normally.

5. 5.Can switch use a double?Show answer

   No.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐if (boolean) { }; else pairs with the nearest if.
• ☐Ladder: first true condition runs; order the conditions carefully.
• ☐switch: int, char, String, byte, short; constant cases; break; default.
• ☐No break → fall through.
• ☐System.exit(0) ends the program at once.
• ☐Ranges or complex conditions → if; fixed choices → switch.

Conditional Statements in Java: frequently asked questions